Compact Waveguide Filtering Power Dividers With Flexible Division Ratio and Enhanced Selectivity

This article proposes a novel design approach for multiport waveguide (WG) filtering power dividers (FPDs) with compact size and enhanced selectivity. A modified cascade trisection (CT) as a basic building block is first investigated allowing for more transmission zeros (TZs) with reduced resonators. Then, the implementation method is given and a bandpass filter (BPF) is designed, where the three poles within the passband are contributed by two rectangular WG (RWG) resonators and a half-wavelength coupling slot connecting them. The coupling slot not only acts as a resonant node but also easily provides intercavity cross-coupling. Besides, the stacked configuration combined with the input/output coaxial feeding scheme enables the enhancement of selectivity by the anticipated two TZs above the passband. An instructive design method for FPDs is proposed, in which the different power divisions mainly depend on the electric field distribution of the fundamental mode of the RWG. Finally, two three-way equal/unequal FPDs with the power division ratios of 1:1:1 and 1:2:1 are simulated, fabricated, and measured. Compared to the reported FPDs, the proposed work demonstrates good features, such as low insertion loss (IL), high selectivity, flexible division ratio, compact size, and high power-handling capability, simultaneously.